Design of a planar power transformer for high voltage, high frequency use

Abstract

A high-voltage (15 kV) power transformer using multilayer printed circuit board (ML-PCB) technology is presented for applications in switched-mode power supplies, whose output power is 4.5 kW, and inverting frequency is 20 kHz. A new configuration for the magnetic core is proposed based on planar EI cores. The parallel connection of planar cores was adopted as a unit, and several units were cascaded to form the high voltage transformer. Manufacturing the PCB involves small tolerances, so the transformer exhibits parasitic effects which are highly reproducible from a production viewpoint. The mechanical configuration of a laboratory prototype is discussed, as well as the electrical, parasitic, and thermal behaviors. The transformer was tested and found to have an efficiency of better than 96%. Compared with traditional high voltage transformers, this transformer has good thermal behavior, good line insulation properties and a high power density.

Design and evaluation of tapped inductors for high-voltage auxiliary power supplies for modular multilevel converters

“…Among these are designs based on coaxial winding arrangements [18] and interleaved planar designs [19].…”

“…Planar transformers allow for good manufacturability also with extensive interleaving which is the main reason for the low leakage possible of planar transformers [20]. The electrical insulation of planar transformers is however not trivial, and although a 15 kV design has been presented [19] the insulation is complex and takes up a prohibitively large part in low power transformers. For realiability, size and cost reasons it would be beneficial to manufacture the tapped inductor using conventional solenoidal inductive component manufacturing methods.…”